Early visual experience plays a very important role in determining the organization of the mature visual system. Various studies have demonstrated that substantial physiological, anatomical, and behavioral effects can result from visual deprivation. Moreover, recent work has shown that a selective visual environment can have limited and predictable physiological consequences. There is evidence that these findings also apply to the human visual system. Experiments are planned to complement the psychophysical studies of the original proposal. Kittens will be reared under various simulated clinical and environmental conditions and subsequent single-unit investigations of visual cortex will be made. The physiological results will be of considerable value in interpreting the psychophysical findings and they may have important applicability to the clinical treatment of vision.